Achtung Penguin! SUSE tunes up Linux for SAP

It seems natural enough that SUSE Linux and SAP would be technical allies; both hail from Germany and both try to peddle business-grade software to enterprises. SAP, which has a huge installed base of Windows customers and a considerable number of Unix customers, cannot be seen to be playing favorites with its OS suppliers just because of nationalism. But it cannot stop – and would not stop – SUSE Linux, the commercial Linux distributor now owned by Attachmate, from making optimizations to its OS stack that make SAP apps run better.

SUSE Linux and SAP cosied up their respective technical support organizations five years ago, and started making tweaks to the SLES stack shortly thereafter on an informal basis, with SLES 10 and the SAP FastTrack installation tool.

In February 2011, SUSE Linux went so far as to launch a special variant of SLES aimed solely at SAP apps, called SLES for SAP Applications, and sitting beside other special versions of SLES like the one aimed to real-time workloads called SUSE Linux Enterprise Real Time, or SLERT for short. That first release tuned for SAP was based on SLES 11 SP1. In February of this year, the company shifted its Linux distro to the Linux 3.0 kernel and rolled out SLES 11 SP2, which among other things included the Btrfs file system and substantial updates to the KVM and Xen server virtualization hypervisors.

It is this latter service pack of SUSE Linux that the new SLES for SAP Apps 11 SP2 is based upon, and it of course inherits all of the attributes of the core SLES 11 SP2 stack as well as getting its own SAP-specific optimizations and enhancements.

The big tweak for the SAP variant of SLES is that the kernel has been tweaked so it can set a hard limit on page caching, explains Jan Weber, product manager for SAP at SUSE Linux. Normally with the Linux kernel, you can indirectly influence the I/O paging behavior of the kernel, but you can't set a hard limit. With SLES for SAP Apps, you can. "This is heavily used by the HANA in-memory database," Weber tells El Reg, and it is one of the reasons why SLES is the exclusive operating system used by SAP to run the HANA software. (HANA doesn't do Windows, even if the vast majority of SAP ERP stacks out there in the world are running on Windows.) Just to be clear: This page caching limit was available with the first release of SLES 11 for SAP Apps SP1 last February and is not new this time around.

The SLES for SAP Apps variant will of course benefit from the many scheduler and memory management enhancements that are built into the Linux 3.0.10 kernel used in plain vanilla SLES 11 SP2. While that regular SLES software runs on Itanium, Power, System z, and x86 processors, the SAP-specific variant is only available on 64-bit Xeon or Opteron servers.

Significantly, SLES 11 SP2 is the release that has been updated to support the latest Xeon E5 processors from Intel and the Opteron 4200 and 6200 processors from Advanced Micro Devices. So if you want SLES to run best in these machines, you need to be at SLES SP2 level. With today's SAP-specific release, now customers deploying ERP stacks or HANA appliances can do so on this newer x86 iron. SLES 11 SP2 can scale to 4,096 cores (or threads if processors have them) and 64TB of main memory, which is by the way, the upper limit on the new UV 2 shared memory server from Silicon Graphics.

The installation wizards for the SAP variant of SUSE Linux have been extended to support NetWeaver middleware and Sybase databases with the SP2 release, and there is also a connector from the open source Clam-AV antivirus software to the SAP software stack now, too.

The SLES 11 for SAP Apps SP2 stack includes the core SLES 11 as well as the High Availability Extensions clustering software. The normal SLES license with priority support costs $1,499 per server per year, and the HA Extensions run another $699 per server per year, for a total of $2,198 per year. The SAP variant has priority support as well as tight integration between the SAP and SLES tech support teams in Germany – plus an 18-month service pack overlap instead of the normal half-year overlap – and will set you back $2,690 per server per year. So the SAP tweaks effectively cost $492 per server per year.

SUSE Linux says that it has over 3,500 customers that run SAP applications on top of its Linux, adding that it has about 70 per cent share of the 5,000 customers worldwide who have chosen Linux as their SAP platform. SAP has something north of 100,000 customers, so Linux has not made a huge dent.

But Kerry Kim, director of solution marketing at SUSE Linux, sees Linux on the rise at SAP, pointing out that Unix sales are on the wane at both Hewlett-Packard and Oracle – and that SAP is looking for something to push back against Oracle's Sparc and x86 engineered systems running SAP or Oracle applications. And HANA is obviously helping there, too. "We are seeing some Windows-to-Linux migrations, but we are seeing more movement from Unix to Linux," Kim says. ®